The Namseong gold and silver deposit is located in the Seolcheon metallogenic province, one of the most important gold production areas in the Republic of Korea. It consists of three gold and silver-bearing quartz veins that fill fractures oriented NW along fault zones in Triassic porphyritic granite. The gold and silver-bearing quartz veins are simple and consist of only one mineralization stage on basis of vein mineralogy and paragenesis. Coarse-grained quartz is found in mainly comb, and partially cockade and cavity-filling textures throughout most of the veins. Wall-rock alteration minerals include sericite, minor pyrite and chlorite. Ore minerals deposited along with electrum include pyrite, sphalerite, chalcopyrite, galena, pyrargyrite, argentite and native silver. Its mineralization age (78.2 ± 1.7 Ma) determined on sericite from wall-rock alteration indicates that the gold and silver mineralization was synchronous with Cretaceous igneous activity. Petrographic examination of textural relationships among sulfides, fluid inclusions, and quartz from one stage shows the genetic relationships between Au-Ag deposition and fluid entrapment. Early wall-rock alteration in one stage was produced and sulfides were deposited from H₂O-NaCl-CO₂ fluids (260-1,700 bar, average 1,000 bar) with Th_total values of 250°C to 380°C and salinities less than about 4 wt.% NaCl. The late sulfides and electrum in one stage were deposited from H₂O-NaCl fluids (100 bar) with Th_total values of 195°C to 331°C and salinities less than about 7 wt.% NaCl. The H₂O-NaCl fluids either evolved through unmixing of H₂O-NaCl-CO₂ fluids or through mixing with circulating meteoric waters as a result of uplift or unloading during mineralization, or both. The deposition of electrum and silver minerals was caused by a decrease in sulfur fugacity/aH₂S/aCl, oxygen fugacity and temperature during wallrock alteration, cooling and dilution produced by mixing of the saline aqueous fluids with meteoric water. The calculated sulfur isotope compositions of hydrothermal fluids from the Namseong deposit (δ³⁴S_H2S = 3.7‰ to 7.2‰) indicate that ore sulfur was derived mainly from a magmatic source but also in part from sulfur contained in the host rocks. The calculated and measured oxygen and hydrogen isotope compositions of the ore-forming fluids (δ¹⁸O_H2O = -2.2‰ to 1.6‰, δD = -83‰ to -64‰) indicate that the fluids were derived from meteoric water and evolved by mixing with local meteoric water and by limited water-rock exchange during mineralization in uplift zones.

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Ore-forming fluid trapped in vein quartz as fluid inclusions from tungsten ore at the Takatori mine was extracted by a crush-leach technique. The trace metal content and isotopic composition (δ⁷Li and ⁸⁷Sr/⁸⁶Sr ratio) of inclusion fluids were measured. Although quartz single crystals can host fluid inclusions associated with different generations, careful selection of analytical samples made it possible to separate the temporal mineralization stages. We succeeded in reconstructing the evolution of the ore-forming fluid from the results of chemical analyses. δ⁷Li values of the ore-forming fluid were between -2.6 and +7.9‰, gradually increasing in the later stages. The early-stage fluid characterized by low δ⁷Li values was derived from magma with a meta-sedimentary source (S-type granite). During precipitation of Li-bearing minerals, the δ⁷Li value of the ore-forming fluid became larger. The initial ⁸⁷Sr/⁸⁶Sr ratio of early-stage ore-forming fluid was 0.7202 to 0.7276, suggesting that the fluid responsible for tungsten mineralization was derived from S-type magma, and this magma had a different origin from the granitic rocks widely distributed in the mining area.

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Geochemical mapping of ⁸⁷Sr/⁸⁶Sr ratios in Shikoku Island and the Kii Peninsula of Southwest Japan was performed using 233 samples of stream sediments (<180 μm). The spatial distribution of ⁸⁷Sr/⁸⁶Sr ratios successively increases from northern to southern geological units, with a gap at the Median Tectonic Line (MTL). In the Inner Zone divided by the MTL, a zone with Cretaceous granitoid rocks of the Ryoke Belt and sedimentary rocks of the Izumi Group, the ⁸⁷Sr/⁸⁶Sr ratios are measured at ~0.710. In the Outer Zone, a zone with Cretaceous metamorphic rocks of the Sanbagawa Belt and Jurassic to Miocene accretionary complexes of the Chichibu Belt and Shimanto Belts, the ⁸⁷Sr/⁸⁶Sr ratios tend to fall in the range from 0.706 to 0.715, tend to increase from north to south, and are highest in the youngest accretionary complex of the Southern Shimanto Belt. The ⁸⁷Rb/⁸⁶Sr-⁸⁷Sr/⁸⁶Sr plots for stream sediments more clearly reveal the differences and similarities of their bedrocks, such as the different trends among the stream sediments of the Inner and Outer Zones. Samples collected from the Inner Zone show almost the same ⁸⁷Rb/⁸⁶Sr-⁸⁷Sr/⁸⁶Sr field as their source rocks, while most of the samples derived from accretionary complexes in the Outer Zone are plotted around a mixing line of older continental detritus and igneous-rock-derived materials. In light of the other geochemical characteristics observed, particularly the REE chemical features of the stream sediments and zircon ages in the basemental sedimentary rocks, the accretionary complexes in the Outer Zone may be mainly formed from the same source rocks, namely, igneous-rock-derived materials and continental detrital materials with different mixing ratios and a larger ratio of continental materials in the Southern Shimanto Belt. This study indicates that ⁸⁷Sr/⁸⁶Sr ratios of stream sediments strongly reflect the isotopic composition of the source rocks and are very useful for distinguishing the various geological and geochemical settings of the source rocks.

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Branched and isoprenoidal glycerol dialkyl glycerol tetraethers (GDGT) are abundant in soils, but little is known about the presence of branched GDGT in rhizosphere-root systems versus bulk soils, and implications of these for GDGT-based climate reconstruction. Here we investigate the archaeal and bacterial communities by studying both core and intact polar GDGT in rhizosphere-root systems of Cinnamomum camphora (Linn) Presl. As well as in litter and some bulk forest soils in Wuhan in central China. The higher abundance of core and intact polar branched GDGT in the rhizoplanes than their associated roots, rhizospheres and bulk soil argue for the presence of heterotrophic branched GDGT-producing bacteria living in direct association with the root surface and feeding on root exudates. In addition, this study showed that the application of the revised calibration (Peterse et al., 2012) produced temperatures closer to the mean annual air temperature than the original global soil calibration (Weijers et al., 2007b). It seems from the similarity of the MBT′ (revised index of methylation of branched tetraethers) and the estimated temperature values that the branched GDGT-producing bacteria in all samples belong to the same community in the studied forest soil.

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A portable gas-analyser was used to perform on-site gas analysis at lakes Nyos and Monoun. Results were used to evaluate the effect of the dissolved CH₄ on the gas saturation level. Although CH₄ represents marginal proportion in term of the total gas concentration (~2.2 mol % in Lake Monoun and ~0.6 mol % in Lake Nyos) it contributes ~37% and ~19% to the total dissolved gas pressure and ~23% and ~13% to saturation level in lakes Monoun and Nyos respectively. The risk due to CH₄ increase is evaluated and monitoring and surveillance measures proposed. Because methane is less more soluble than carbon dioxide, its increase may accelerate saturation of the lake waters with dissolved gas making gas eruptions more frequent. It is therefore recommended to regularly monitor the lakes in order to assess CH₄ evolution for hazard mitigation purposes. If future monitoring surveys confirm current CH₄ increase, a device to extract deep rich-gas water must be experimented and put in place without delay.

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This study investigated arsenic (As) concentrations in existing drinking water sources in Hanam province, Vietnam. Sand-filtered groundwater, piped water, raw groundwater, and a type of drinking water mostly sourced from rainwater (hereafter referred to as the “stored rainwater”) are commonly used for drinking purposes in this area. It was found that all water sources contained different levels of toxic As. The highest levels were found in raw groundwater, followed by sand-filtered water, piped water, and stored rainwater. More than 50% of the stored rainwater samples contained As levels above the WHO recommendation value. As such, the daily As uptake in local residents from this kind of stored rainwater may be larger than previously considered because they consume stored rainwater as an alternative drinking water source. Relatively high levels of As in the stored rainwater samples also suggested that residents possibly mix rain and groundwater in rainwater containers in order to meet their daily water demand.

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We present analytical protocols and the analytical performance of Pb isotope analysis of silicate minerals and rocks at the Pb = 0.02-15 ppm level using excimer laser ablation (LA) coupled with an enhanced-sensitivity multiple collector-inductively coupled plasma mass spectrometer (MC-ICP-MS). We applied Faraday cups for all the isotopes analysed, including the minor isotopes ²⁰⁴Pb and ²⁰⁴Hg. This device is, so far, the first attempt to analyse samples with low Pb concentrations by LA-MC-ICP-MS. The improved sensitivity of the mass spectrometer, along with careful correction of the Hg overlap on ²⁰⁴Pb, permits accurate analyses of ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, and ²⁰⁸Pb/²⁰⁴Pb ratios. This procedure includes determination of the fractionation factor of Hg isotopes among ²⁰⁰Hg, ²⁰²Hg, and ²⁰⁴Hg. The analytical error, including precision and reproducibility, was within 1.5 per mil for 5-15 ppm Pb in glassy silicate rocks (groundmass) taken from 500 μm × 500 μm × 100 μm (0.025 mm³) craters. These results were comparable to those obtained using conventional non-spiked thermal ionization mass spectrometry after chemical separation. Major Pb isotope ratios, including ²⁰⁷Pb/²⁰⁶Pb and ²⁰⁸Pb/²⁰⁶Pb, were also analysed to within a 1 per mil error for 1-1.5 ppm Pb in groundmass and plagioclase crystals from craters 200 μm in diameter and 100 μm deep. When a larger sample size, i.e., a 500 μm × 500 μm × 200 μm crater was used, a ~10 per mil error was achievable for samples containing ~0.02 ppm Pb, which allows in situ analysis of low-Pb minerals such as clinopyroxene. Melt (glass) inclusions in olivine with a sample size of diameter ~200 μm containing 1-5 ppm Pb were also analysed with 1-10 per mil errors. The achievable accuracy and precision were significantly better for ²⁰⁷Pb/²⁰⁶Pb and ²⁰⁸Pb/²⁰⁶Pb, and better for ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, and ²⁰⁸Pb/²⁰⁴Pb than those obtained by in situ analyses using secondary ion microprobe mass spectrometry and a normal-sensitivity LA-MC-ICP-MS using one or more ion counters. The analytical performance of the present method is useful for many applications connected with geochemical studies on igneous rocks. We present examples for groundmass, plagioclase, clinopyroxene, and olivine melt inclusion analyses of ocean island basalts.

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Oxygen isotope values of low-growth coral (<5 mm/yr) skeletons may reflect kinetic effects, which is problematic for sea surface temperature (SST) reconstruction. Here, we report a Sr/Ca-based SST reconstruction for a temperate Porites coral collected from Kyushu, Japan, near the northern latitudinal extent of hermatypic corals. Results indicate that Sr/Ca variations in a low-growth coral remain independent from growth rate, in contrast to the oxygen isotope ratios of the same coral.

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